Modulating anodic performance of halophilic electroactive microbial consortia with selective enrichment using metal-based terminal electron acceptors

Abstract

Long start-up times and lack of robust halophilic electroactive microbes (EAM) challenge the implementation of microbial fuel cells (MFC) for treating saline wastewater. Here a pragmatic strategy is presented to selectively enrich halophilic EAM consortium capitalising on their cellular respiration process using graphene oxide (GO) and metal ions (Fe3+, Mn4+ and Cu2+) as the primary and secondary terminal electron acceptors (TEA), respectively. Enrichment of GO-respiring EAM consortium with Fe3+ ions enabled growth of an efficient anodic biofilm within a short start-up time of 50 h and generated up to 1.1 W/m3 while treating highly saline electrolyte (2 % NaCl). In conjunction with predictive genetic profiling, in-depth electrochemical analysis of the biofilm unravelled key mechanisms of direct extracellular electron transfer for generating high anodic currents. Additionally, the inclusion of Fe3+ ions as secondary TEA upregulated the metabolic activity of GO-respiring EAM, which subsequently influenced their anodic performance rather than the relative abundance of exoelectrogens in the biofilm. Thus, this study stimulates the discovery of novel EAM communities using an advanced and sensible design of selective media by varying the electron donor and TEA couplings.